This invention relates to video systems and more particularly to digital video.
Presently, there is extensive interest in advanced video services using technologies of digital signal processing, VLSI, and packet networkings. Examples of these services include video on the Internet, videoconferencing, interactive network video, video editing/publishing, and virtual video library/store. For many digital video applications, compressed video bitstreams are usually transmitted over networks and/or stored in tapes or databases in Common Intermediate Format (CIF) or Quarter Common Intermediate Format (QCIF).
Various digital video applications utilize CIF and QCIF digital formats. For example, in multi-point videoconferencing over networks, multi-point control unit (MCU) receives QCIF compressed video bitstreams from several users, combines them into one CIF video, down converts it into QCIF video, encodes it, and sends the QCIF video bitstream to all the users. There is a need to down convert a CIF compressed video to a QCIF video bitstream to provide compatibility between the various digital video sources and application uses.
The present invention is a system and method to convert a CIF compressed video to a QCIF video bitstream. A coding mode and a motion vector for a macroblock in a QCIF video sequence are selected from those of a corresponding CIF video sequence without motion estimation.